Plasma sterilizing with downstream oxygen addition

Abstract

A method for plasma sterilization includes forming a gas plasma from a substantially oxygen-free mixture containing argon or helium and from 1% to 5% (v/v) hydrogen in a plasma generating chamber, and exposing an article to be sterilized in a sterilizing chamber to a non-explosive mixture of the plasma gas and from 1% up to 20% (v/v) oxygen gas. Preferably, the pressure in the sterilizing chamber is from 0.1 to 10 torr and the chamber temperature is less than 6° C., the mixture from which the plasma is generated contains from 4% to 5% (v/v) hydrogen, and the article in the sterilizing chamber is exposed to a mixture of plasma gas and from 1% to 10% (v/v) oxygen.

We claim: 
     
       1. A method for plasma sterilization comprising exposing an article in a sterilizing chamber under a preselected temperature to a non-explosive mixture of 1% to 20% (v/v) oxygen and a gas plasma until the article is sterilized, said gas plasma being generated by a plasma generation means from a mixture of 1% to 20% (v/v) hydrogen and an inert gas at a pressure of from 0.1 to 10 torr, and said non-explosive mixture of oxygen being introduced downstream of said gas plasma generation means. 
     
     
       2. A method of claim I wherein the oxygen concentration is from 1% to 10% (v/v) oxygen. 
     
     
       3. A method of claim 2 wherein the hydrogen concentration is from 1% to 5% (v/v). 
     
     
       4. A method of claim 1 wherein the pressure in the sterilizing chamber is from 1 to 10 torr. 
     
     
       5. A method of claim 1 wherein the article is enclosed in a package including a porous organic layer, and the preselected temperature is up to 60° C. 
     
     
       6. A method of claim 6 wherein the porous organic layer contains cellulose or an organic polymer. 
     
     
       7. A method of claim 1 wherein the article is metal and the preselected temperature is up to 80° C. 
     
     
       8. A method for sterilization of an article comprising the steps of: generating a plasma stream in a plasma generating chamber by subjecting a gas mixture stream to a plasma inducing means;   combining an oxygen or oxygen containing stream with said plasma stream downstream from the plasma inducing means; and   exposing the article to the combined plasma stream and oxygen or oxygen containing stream in a sterilization chamber to effect sterilization.   
     
     
       9. A method for sterilization of an article as in claim 8, wherein said gas mixture stream includes a non-explosive mixture of oxygen. 
     
     
       10. A method of claim 8 wherein the article is enclosed in a package including a porous organic layer, and the preselected temperature is up to 60° C. 
     
     
       11. A method of claim 10 wherein the porous organic layer contains cellulose or an organic polymer.